So, although it may not be a trivial exercise to add in this package to R and then to interface with Mathematica using RLink, it may be simpler than trying to write some kind of seg-y parsing code in regular Mathematica.

If you mean the SEGY seismic data format I can recomend to use this project
https://github.com/KirillBelovTest/CustomImportExport
This package allows you to import and export seismic data into the Mathematica, to work with the trace headers and text headers. It supports both the data format floating-point and integer data.
You can dowload repository and find some examples. The comments are on Russian but a think you can understand the code easily.
If you would like to improve this project, can you tell us about your wishes and to participate in development.

Thank you Anton for sharing these codes with me. This is exactly what I need, to be able to read SEGY data into the Mathematica. However, I will appreciate if you could help with English version of step-by-step guide to use it. I am a new user of Mathematica. Thank you once again

Thank you for sharing this interesting body of work. I installed the package as per the instructions and am exploring the examples. As it happens the first one I tried, from the file "ExampleOfUse.md" has a minor issue. The code:

Dear Anton,
I am working on velocity analysis (stacking velocity) using mathematica. However, I applied my code on the traces but it did not work. Of course I know why it did not work because my data has to be in CMP. Can the customExport expository do sorting? If not could you please advice on how to sort my data into CMP.
Thank you.

Hi people!
I am trying to understand what some commands does in Mathematica but I do not understand yet. I have attached the code to this write u[. I know what each of the terms means but I need to understand what each command does. I want to know how the command will perform each function.